Light Emitting Diode Chip

ABSTRACT

A light emitting diode chip including a substrate and a light emitting diode element layer is provided. The substrate has a growth surface and a plurality of microstructures on the growth surface. An area of the growth surface occupied by the microstructures is A1 and an area of the growth surface not occupied by the microstructures is A2, such that A1 and A2 satisfy the relation of 0.1≦A2/(A1+A2)≦0.5. The light emitting diode element layer is disposed on the growth surface of the substrate.

CROSS-REFERENCES TO RELATED APPLICATIONS

The present disclosure is part of a continuation application claimingthe priority benefit of U.S. patent application Ser. No. 14/521,471,filed on Oct. 23, 2014, which claims the priority benefits of Taiwanapplication serial no. 103117640, filed on May 20, 2014, and Taiwanapplication serial no. 103208802, filed on May 20, 2014. The entirety ofeach of the above-mentioned patent applications is hereby incorporatedby reference herein and made a part of the present disclosure.

TECHNICAL FIELD

The disclosure relates to a light emitting diode chip and moreparticularly to a light emitting diode chip with favorable lightextraction efficiency.

BACKGROUND

Along with the advancement of the semiconductor technology, lightemitting diodes now have the advantages of high brightness output, lowpower consumption, compactness, low driving voltage, mercury free.Therefore, the LED has been extensively applied in the field of displaysand illumination.

A light emitting diode structure typically includes a light emittingdiode chip and a peripheral wiring, and the light emitting diode chiptypically includes a growth substrate and a semiconductor element layer.In general, the light emitting efficiency and the light extractionefficiency of a light emitting diode chip are related.

SUMMARY

An exemplary embodiment of the disclosure provides a light emittingdiode chip that offers favorable light extraction efficiency.

An exemplary embodiment of the disclosure provides a light emittingdiode emitting diode chip that includes a substrate and a light emittingdiode element layer. The substrate includes a growth surface and aplurality of microstructures located on the growth surface, wherein thearea of the growth surface occupied by these microstructures is A1 andthe area of the growth surface not occupied by these microstructures isA2, and A1 and A2 satisfy the relation: 0.1≦A2/(A1+A2)≦0.5. The lightemitting element layer is disposed on the growth surface of thesubstrate.

According to an exemplary embodiment of the disclosure, wherein theplurality of microstructures includes a plurality of protrusions.

According to an exemplary embodiment of the disclosure, wherein theheight of each protrusion is between 1 micron and 3 microns.

According to an exemplary embodiment of the disclosure, wherein theheight of each protrusion is between 1.2 micron and 2 microns.

According to an exemplary embodiment of the disclosure, wherein eachprotrusion has a base connecting with the growth surface and the basehas a width, and two neighboring bases maintain a distance therebetween,and a sum of the width and the distance is between 1 micron and 3microns.

According to an exemplary embodiment of the disclosure, wherein thedistance between the centroids of two neighboring bases is between 1micron and 3 microns.

According to an exemplary embodiment of the disclosure, each protrusionof has a plurality of sectional surfaces parallel to the growth surface,and the areas of the plurality of sectional surfaces progressivelydecrease along the height direction of the protrusion.

According to an exemplary embodiment of the disclosure, the areas of theplurality of sectional surfaces linearly decrease along the heightdirection of each protrusion.

According to an exemplary embodiment of the disclosure, the areas of theplurality of sectional surfaces decrease non-linearly along the heightdirection of each protrusion.

According to an exemplary embodiment of the disclosure, the plurality ofmicrostructures includes a plurality of depressions.

According to an exemplary embodiment of the disclosure, the depth ofeach depression is between 1 micron and 3 microns.

According to an exemplary embodiment of the disclosure, the depth ofeach depression is between 1.2 micron and 2 microns

According to an exemplary embodiment of the disclosure, each depressionhas an opening connecting with the growth surface and the opening has awidth. The two neighboring openings maintain a distance therebetween,and a sum of the width and the distance is between 1 micron and 3microns.

According to an exemplary embodiment of the disclosure, the distancebetween the centroids of the two neighboring openings is between 1micron and 3 microns.

According to an exemplary embodiment of the disclosure, each depressionhas a plurality of sectional surfaces parallel to the growth surface,and areas of the plurality of sectional surfaces progressively decreasealong a depth direction of the depression.

According to an exemplary embodiment of the disclosure, the areas of theplurality of sectional surfaces linearly decrease along the heightdirection of the depression.

According to an exemplary embodiment of the disclosure, the above lightemitting diode element layer further includes a first conductivity typesemiconductor layer, a light emitting layer and a second conductivitytype semiconductor layer. The first conductivity type semiconductorlayer is disposed on the growth surface. The light emitting layer isdisposed on the first conductivity type semiconductor layer. The secondconductivity type semiconductor layer is disposed on the light emittinglayer.

According to an exemplary embodiment of the disclosure, the above lightemitting diode element layer further includes a buffer layer disposed onthe growth surface. The buffer layer is configured between the substrateand the first conductivity type semiconductor layer and encapsulates theplurality of protrusions.

According to an exemplary embodiment of the disclosure, a material ofthe above buffer layer includes, but is not limited to, aluminumnitride, gallium nitride, indium nitride, aluminum indium nitride,aluminum gallium nitride, aluminum gallium indium nitride, zirconiumboride, or hafnium nitride.

According to an exemplary embodiment of the disclosure, one of the firstconductivity type semiconductor layer and the second conductivity typesemiconductor layer is a P-type semiconductor layer and another one ofthe first conductivity type semiconductor layer and the secondconductivity type semiconductor layer is an N-type semiconductor layer.

According to an exemplary embodiment of the disclosure, the lightemitting diode element layer further includes a first electrodeelectrically connected with the first conductivity type semiconductorlayer and a second electrode electrically connected with the secondconductivity type semiconductor layer.

According to an exemplary embodiment of the disclosure, the lightemitting diode element layer further includes a transparent conductivelayer disposed on the second conductivity type semiconductor layer, andthe second electrode is electrically connected with the secondconductivity type conductor layer through the transparent conductivelayer.

According to an exemplary embodiment of the disclosure, the lightemitting diode element layer further includes a reflective layer,disposed on the transparent conductive layer, and the transparentconductive layer is disposed between the reflective layer and the secondconductivity type conductive layer.

According to an exemplary embodiment of the disclosure, the lightemitting diode layer comprises a single quantum well structure or amultiple quantum well structure.

According to an exemplary embodiment of the disclosure, the surfaceroughness of the surface of the microstructure and the grow surface doesnot exceed 10 nanometers.

According to the exemplary embodiments of the disclosure, the growthsurface of the substrate of the light emitting diode chip has aplurality of microstructures thereon, wherein the ratio of the area ofthe growth surface not covered by these microstructures to the totalarea of the growth surface is between 0.1 and 0.5. Accordingly, theprobability that the light being scattered is increased to furtherimprove the light extraction efficiency of the light emitting diodechip.

A light emitting diode chip comprising a substrate and a light emittingdiode element layer is provided. The substrate comprises a growthsurface and a plurality of microstructures on the growth surface. Asurface roughness of the growth surface does not exceed 10 nanometers. Alight emitting diode element layer is disposed on the growth surface.

A method of fabricating a light emitting diode chip is provided.Firstly, a substrate is provided. The substrate comprises a growthsurface and a plurality of microstructures on the growth surface. Afirst area of the growth surface occupied by the plurality ofmicrostructures is A1 and a second area of the growth surface notoccupied by the plurality of microstructures is A2. A1 and A2 satisfythe relation 0.1≦A2/(A1+A2)≦0.5. Then, a light emitting diode elementlayer is disposed on the substrate.

A method of fabricating a light emitting diode chip is provided.Firstly, a surface treatment is performed on a substrate to form agrowth surface and a plurality of microstructures on the growth surface.A first area of the growth surface occupied by the plurality ofmicrostructures is A1 and a second area of the growth surface notoccupied by the plurality of microstructures is A2. A1 and A2 satisfythe relation 0.1≦A2/(A1+A2)≦0.5. Then, a light emitting diode elementlayer is disposed on the substrate.

A light emitting diode chip comprising a substrate and a light emittingdiode element layer is provided. The substrate comprises a plurality ofrecesses and a plurality of protrusions. The plurality of theprotrusions are connected between the plurality of the recesses. A lightemitting diode element layer is disposed on the plurality of therecesses and the plurality of the protrusions. A surface roughness of asurface of one of the recesses does not exceed 10 nanometers.

A surface roughness of a surface of one of the protrusions does notexceed 10 nanometers.

The light emitting diode chip comprises a flip-chip light emitting diode(LED) chip, or a vertical type light emitting diode (LED) chip, or ahorizontal type light emitting diode (LED) chip

Several exemplary embodiments are described in detail below to furtherdescribe the disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of the invention, and are incorporated in and constitute apart of this specification. The drawings illustrate embodiments of theinvention and, together with the description, serve to explain theprinciples of the invention.

FIG. 1 is a schematic diagram of a light emitting diode chip accordingto an exemplary embodiment of the disclosure.

FIG. 2 is a partial top view of a growth substrate of FIG. 1.

FIG. 3 is schematic diagram of a light emitting diode chip of acomparative example of the disclosure.

FIG. 4 is a diagram illustrating the test result of the light extractionefficiency of the light emitting diode chip of FIG. 1.

FIG. 5 is a schematic diagram of a light emitting diode chip of anotherexemplary embodiment of the disclosure.

FIG. 6 is a partial top view diagram of the growth substrate of FIG. 5.

FIG. 7 is a diagram illustrating the test result of the light extractionefficiency of the light emitting diode chip of FIG. 5.

FIG. 8 is a diagram illustrating another test result of the lightextraction efficiency of the light emitting diode chip of FIG. 5.

FIG. 9 is a schematic diagram of a light emitting diode chip accordingto another exemplary embodiment of the disclosure.

FIG. 10 is a schematic diagram of a light emitting diode chip accordingto another exemplary embodiment of the disclosure.

FIG. 11 is a schematic diagram of a light emitting diode chip of anothercomparative example of the disclosure.

FIG. 12 is a schematic diagram of a light emitting diode chip of anotherexemplary embodiment of the disclosure.

FIG. 13 is a partial top view diagram of a growth substrate in FIG. 12.

FIG. 14 is schematic diagram of a light emitting diode chip of anotherexemplary embodiment of the disclosure.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 is a schematic diagram of a light emitting diode chip accordingto an exemplary embodiment of the disclosure. Referring to FIG. 1, thelight emitting diode chip 100 of the disclosure includes a substrate 110and a light emitting diode element layer 120. In general, the substrate110 may be sapphire (aluminum oxide Al2O3) substrate, silicon carbide(SiC) substrate, silicon (Si) substrate, gallium arsenide (GaAs)substrate, gallium phosphide (GaP) substrate, gallium nitride (GaN)substrate, lithium aluminum oxide (LiAlO2) substrate or other substratethat is appropriate for epitaxy.

The substrate 110, constructed with the above material for example andhaving a growth surface 111 and a plurality of microstructuresconfiguring at the growth surface 111, is formed via a patterningprocess, wherein these microstructures are protrusions 112, for example.Typically, the patterning of the substrate 110 is achieved byphotolithograph and etching process. More particularly, a photoresist isused to define the pattern to be transferred to the substrate 110,followed removing a portion of the substrate 110 through a dry etchingor wet etching process to form the protrusions 112 on the substrate 110surface. It should be understood that the patterning of the substrate110 is presented by way of examples and not by way of limitation. Inother exemplary embodiments, a surface treatment is performed to renderthe surface of each protrusion 112 and the growth surface 111 with anappropriate degree of roughness. In principle, the surface roughness ofthe surface of each protrusion 112 and the growth surface 111 does notexceed the roughness value of 10 nm. When the surface roughness of thesurface of each protrusion 112 and the growth surface does not exceed 10nm, the epitaxy quality of the light emitting diode element layer 120 isimproved to ensure the light emitting efficiency of the light emittingdiode chip 100.

In this exemplary embodiment, the height H of each protrusion 112 isbetween 1 micron and 3 microns. In another exemplary embodiment, theheight is between 1.2 micron and 2 microns. When the heights H of eachprotrusion 112 is too high, epitaxy of the light emitting diode elementlayers may be difficult. When the height H of each protrusion 112 is toolow, an adverse light extracting efficiency of the photon is resulted.Moreover, the thickness of the substrate 110 is between about 50 micronsand about 500 microns. The thickness of the substrate 110 herein doesnot include the height of each protrusion 112.

Still referring to FIG. 1, the light emitting diode element layer 120 isdisposed on the growth surface 111 of the substrate 110. In thisexemplary embodiment, the light emitting diode element layer 120includes a first conductivity type semiconductor layer 121, a lightemitting layer 122 and a second semiconductor layer 123, wherein thefirst conductivity type semiconductor layer 121 is disposed on thegrowth surface 111, the light emitting layer 122 is disposed on thefirst conductivity type semiconductor layer 121 and the secondconductivity type semiconductor layer 123 is disposed on the lightemitting layer 122. Typically, the first conductivity type semiconductorlayer 121, and the light emitting layer 122 and the second conductivitytype semiconductor layer 123 are fabricated by metal organic chemicalvapor deposition (MOCVD); however, it should be understood that thefabrication method of the above layers is presented by way of examplesand not by way of limitation.

Further, one of the first conductivity type semiconductor layer 121 andthe second conductivity type semiconductor layer 123 is a P-typesemiconductor layer, while another one of the first conductivity typesemiconductor layer 121 and the second conductivity type semiconductorlayer 123 is an N-type semiconductor layer. In this exemplaryembodiment, the first conductivity type semiconductor layer 121 is anN-type gallium nitride layer doped with silicon, germanium, antimony ora combination thereof, while the second conductivity type semiconductorlayer 12 is a P-type gallium nitride layer doped with magnesium.Further, the thickness of the first conductivity type semiconductorlayer 121 is between about 2 microns and 6 microns, while the thicknessof the second conductivity type semiconductor layer 123 is between about0.1 micron and 0.5 micron.

In one exemplary embodiment, the light emitting layer 122 is constructedwith, for example, a single or multiple quantum well structure ofaluminum gallium indium nitride, wherein the thickness of the lightemitting layer 122 is between about 0.05 micron and 0.3 micron.Moreover, the light emitting diode element layer 120 also includes abuffer layer 124, a first electrode 125, a second electrode 126 and atransparent conductive layer 127. The buffer layer 124 is disposed onthe growth surface 111 and is configured between the substrate 110 andthe first conductivity type semiconductor layer 121 for mitigating thelattice mismatch phenomenon resulted from the disparity in the latticeconstants between the first conductivity type semiconductor layer 121and the substrate 110. The buffer layer 124 improves the epitaxy qualityof the first conductivity type semiconductor layer 121, the lightemitting layer 122 and the second conductivity type semiconductor layer123; hence, the light extraction efficiency of the light emitting diodechip 100 is precluded from being affected.

In this exemplary embodiment, the protrusions 112 configured on thegrowth surface 111 are encapsulated by the buffer layer 124, wherein thethickness of the buffer layer 124 is between about 0.01 micron and 0.1micron. Typically, the material of the buffer layer 124 includes, but isnot limited to, aluminum nitride, gallium nitride, indium nitride,aluminum indium nitride, aluminum gallium nitride, aluminum galliumindium nitride, zirconium boride, or hafnium nitride.

Further, the first electrode 125 is disposed on and is electricallyconnected with the first conductivity type semiconductor layer 121. Thesecond electrode 126 and the transparent conductive layer 127 are bothdisposed on and are electrically connected with the second conductivitytype semiconductor layer 123, wherein the second electrode 126, forexample, is electrically connected with the second conductivity typesemiconductor layer 123 through the transparent conductive layer 127. Ingeneral, the first electrode 125 and the second electrode 126 areconstructed with a metal having good electrical conductivity, such asgold, aluminum or silver or an alloy thereof. Further, the material ofthe transparent conductive layer 127 is, for example, a single layer ormultiple layers of metal with an overall thickness being less than 0.03micron. Also, metal oxide, for example, indium tin oxide (ITO) or indiumzinc oxide (IZO), may also be selected for the material of thetransparent conductive layer 127, wherein the thickness of thetransparent conductive layer 127 formed with metal oxide is between 0.03micron and 0.3 micron.

FIG. 2 is a partial top view diagram of the growth substrate of FIG. 1.Referring to both FIGS. 1 and 2, the area of the growth surface 111occupied by the protrusions 112 is A1 and the area of the growth surfacenot occupied by the protrusions 112 is A2, wherein A1, A2 satisfy thefollowing relation: 0.1≦A2/(A1+A2)≦0.5, and A2/(A1+A2) is defined as thefilling ratio.

More specifically, each protrusion 112 has a base 113 connecting withthe growth surface 111, and the base 113 has a width W. Herein, eachprotrusion 112 has a plurality of sectional surfaces SEC (one of whichis schematically depicted in FIG. 1) parallel to the growth surface 111,wherein the areas of the sectional surfaces SEC progressively decreases,for example linearly decreases from the base 113, along the heightdirection D. In this exemplary embodiment, each protrusion 112 has, forexample, a cone shape, with a circular base 113, and the diameter of thebase is the width W. It should be noted that the application is notlimited as such. In other exemplary embodiments, the base of theprotrusions 112 may have other shapes, for example, oval, triangular,rectangular or polygonal, which can be attuned according to the actualdesign requirements.

A distance S is maintained between two neighboring bases 113, and thesum of the width W and the distance S is a fixed value, ranging between1 micron and 3 microns. The following disclosure is exemplified by thesum of the width W and the distance S being 3 microns. The sum of thewidth W and the distance S is substantially identical to the distance Gbetween the centroids C of two neighboring bases 113. Since the sum ofthe width W and the distance S is a fixed value, changes in the width Wand the distance S affect the value of the filling ratio (which isA2/(A1+A2)). Alternatively speaking, when the width W increases, thedistance S correspondingly decreases. Consequently, the area of thegrowth surface 111 occupied by the protrusions 112 increases and thearea of the growth surface 111 not occupied by the protrusions 112decreases to reduce the filling ratio. As the filling ratio becomessmaller, the light emitted from the light emitting layer 122 iseffectively scattered by these protrusions 112; hence, the probabilityof photons encountering a totally internal reflection (TIR) inside thelight emitting diode chip 112 is lower to thereby enhance the lightextraction efficiency of the light emitting diode chip 100.

FIG. 3 is a schematic diagram of a light emitting diode chip of acomparative example of the disclosure. Referring to FIG. 3, the lightemitting diode chip 100A in a comparative example and the previouslydisclosed light emitting diode chip 100 are substantially the same, themajor difference between the two lies in that the light emitting diodechip 100A does not have a patterned surface on the substrate 110 a;instead, the light emitting diode chip 100A has a planar surface. Acomparison in the light extraction efficiency between the light emittingdiode chip 100A and the light emitting diode chip 100 is describedhereafter. The output power of the light emitted by the light emittingdiode chip 100 is P and the output power of the light emitted by thelight emitting diode chip 100A is P1. The equation used in calculatingthe enhancement of the output power of the light emitting chip 100 is(P−P1)/P1.

The light extraction efficiency test of the light emitting chip 100 isconducted based on four groups of parameters, wherein the filling ratiocorresponding to the width W and the distance S of each group istabulated in Table 1. According to the above disclosure, as the width Wincreases, the distance S and the filling ratio correspondinglydecrease.

TABLE 1 1^(st) Group 2^(nd) Group 3^(rd) Group 4^(th) Group Distance S(μm) 0.1 0.3 0.5 0.7 Width W(μm) 2.9 2.7 2.5 2.3 Filling Ratio (%) 18%29% 39% 48%

FIG. 4 is a diagram illustrating the test result of the light extractionefficiency of the light emitting diode chip of FIG. 1, wherein thevertical axis represents enhancement, while the horizontal axisrepresents the heights H of the protrusions 112. Referring to FIG. 4,lines S1 to S4 respectively represent the enhancement of lightextraction efficiency of the light emitting diode chip 100 under thefirst to the fourth group of parameter settings. Under the conditionsthat A1 and A2 satisfying the relation of 0.1≦A2/(A1+A2)≦0.5, the lightextraction efficiency of the light emitting diode chip 100 iseffectively enhanced, wherein the enhancement of the output power of thelight emitting diode chip 100 is even more apparent when the fillingratio is 18%. The enhancement of the output power under the same groupof parameter settings, in which the width W and the distance S are fixedsuch that the area A1 of the growth surface occupied by theseprotrusions 112 and the area A2 of the growth surface not occupied bythese protrusions 112 remain unchanged, will be described herein withreference to the filling ratio of 18%. The test is conducted by varyingthe heights H (1.2 μm, 1.6 μm, 1.8 μm and 2.0 μm) of the protrusions.When the heights H of the protrusions 112 range between 1.2 μm and 2.0μm, the enhancement of the output power of the light emitting diode chip100 correspondingly increases as the heights H increase.

Reference will now be made in detail to other embodiments of theapplication. Whenever possible, components that are the same as orsimilar to those of the previous embodiment are assigned with the samereference numerals, and descriptions thereof will be omittedhereinafter.

FIG. 5 is a schematic diagram of a light emitting diode chip of anotherexemplary embodiment of the disclosure. FIG. 6 is a partial top viewdiagram of the growth substrate of FIG. 5. Referring to both FIGS. 5 and6, the light emitting diode chip 100 b and the light emitting diode chip100 are substantially the same. A major difference between the two liesin that the protrusions 115 on the growth surface 114 of the substrate110 b are not cone-shaped, but closer to bullet-like shaped.Alternatively speaking, the areas of the sectional surfaces SEC of eachprotrusion 115 (one of which is schematically depicted in FIG. 5) do notlinearly decrease along the height direction. Alternatively speaking,the decreasing rate of the areas of the sectional surfaces SEC1 of eachprotrusion 115 increases as the height increases. In this exemplaryembodiment, the base 116 of each protrusion 115 is circular, forexample, and the width W is basically the diameter of the base 116.However, it should be understood that the application is not limited toany of the exemplary embodiments, and various modifications oralterations may be made without departing from the spirit of theinvention. In other exemplary embodiments, the shape of the protrusionbase can be oval, rectangular or polygonal, and be modified based onactual design requirements.

FIG. 7 is a diagram illustrating the test result of the light extractionefficiency of the light emitting diode chip of FIG. 5, wherein thevertical axis represents the enhancement, while the horizontal axisrepresents the heights H of the protrusions 115. Referring to FIG. 7,the light extraction efficiency of the light emitting diode chip 100B iscompared with the light extraction efficiency of the light emittingdiode chip 100A, wherein the parameter settings, the test method andenhancement calculation method can be referred to the previousembodiments, and the descriptions thereof are omitted hereinafter.

The lines S5 to S8 represent the enhancement of the output power of thelight emitting diode chip 100B respectively under the first to thefourth parameter settings. More specifically, under the conditions thatA1 and A2 satisfy the relation of 0.1≦A2/(A1+A2)≦0.5, the lightextraction efficiency of the light emitting diode chip 1008 iseffectively enhanced, wherein the enhancement of the output power of thelight emitting diode chip 100B is most apparent when the filling ratiois 18%. The enhancement of the output power under the same group ofparameter settings, meaning that the width W and the distance S arefixed such that the area A1 of the growth surface occupied by theseprotrusions 112 and the area A2 of the growth surface not occupied bythese protrusions 112 remain unchanged, will be detailed herein withreference to the filling ratio of 18%. The test is conducted by varyingthe heights H (1.2 μm, 1.6 μm, 1.8 μm and 2.0 μm) of the protrusions.When the heights H of the protrusions 112 ranges between 1.2 μm and 2.0μm, the enhancement of the output power of the light emitting diode chip100B correspondingly increases as the heights H increase.

FIG. 8 a diagram illustrating another test result of the lightextraction efficiency of the light emitting diode chip of FIG. 5,wherein the vertical axis represents enhancement, while the horizontalaxis represents the heights H of the protrusions 115. Referring to FIG.8, the test of light extraction efficiency of the light emitting diodechip 100B is performed respectively based on two groups of parametersettings. The first group parameter settings is that the width of thebase 116 of each protrusion 115 is fixed at 2.5 microns, the distance Sis fixed at 0.1 micron and the filling ratio is 22.5%. The second groupparameter settings is that the width of the base 116 of the protrusion115 is fixed at 2.5 micron, the distance S is fixed at 0.7 micron andthe filling ratio is 47.1%.

Under the premise that the width W is fixed and the distance S graduallyreduces, the number of protrusions 115 increases correspondingly; hence,the number of protrusions 115 under the first group of parametersettings is greater than the number of protrusions 115 under the secondgroup of parameter settings. Alternatively speaking, under the firstgroup of parameter settings, the area of the growth surface 111 boccupied by these protrusions 115 increases, while the area of thegrowth surface 111 b not occupied by these protrusions 115 decreases toreduce the filling ratio.

The lines S9, S10 represent the enhancement of the output power of thelight emitting diode chip 100B respectively under the first group ofparameter settings and the second group of parameter settings, whereinthe heights of the protrusions is adjusted from 1.2 μm to 2.2 μm. Thelines L1, L2 respectively represent the liner fit of the lines S9, S10.As shown in FIG. 8, as the filling ratio becomes smaller, the heights Hof the protrusions 115 increase and the enhancement of the output powerof the light emitting diode 100B is substantially reflected from theinclining trend.

The lights emitted from the light emitting diode chip 100, 100B and thelight emitting diode chip 100A of the comparative example are actuallyemitted to the outside through the transparent conductive layer 127. Incomparison, the light emitted from a flip-chip LED chip is emitted tothe outside through a substrate. Based on the similar design principleof the above exemplary embodiments, favorable light extractionefficiency is achieved if the growth surface of the flip-chip LED chipsubstrate also comprises a plurality of protrusions, which isexemplified by the following embodiments. Whenever possible, componentsthat are the same as those of the previous embodiment are assigned withthe same reference numerals, and descriptions thereof will be omittedhereinafter.

FIG. 9 is a schematic diagram of a light emitting diode chip accordingto another exemplary embodiment of the disclosure. Referring to FIG. 9,the light emitting diode chip 100C is, for example, a flip-chip LEDchip, and is substantially the same as the light emitting diode chip100. A major difference between the two lies in that the light of thelight emitting diode chip 100C is emitted in a direction such that thelight passes to the outside substantially through the substrate 110.Accordingly, in this exemplary embodiment, the light emitting diodeelement layer 120 a further includes a reflective layer 128. Thereflective layer 128 is disposed on the transparent conductive layer127, and the transparent conductive layer 127 is positioned between thereflective layer 128 and the second conductivity type semiconductorlayer 123. Generally speaking, the material of the reflective layer 128may include silver, aluminum, or other metals with desired reflectiveproperty. When the light emitted from the light emitting layer 122 isirradiated to the reflective layer 128, the light is reflected and thentransmitted toward the substrate 110.

FIG. 10 is a schematic diagram of a light emitting diode chip accordingto another exemplary embodiment of the disclosure. Referring to FIG. 10,the light emitting diode chip 100D and the light emitting diode chip100C are substantially the same. A major difference between the two liesin that the protrusions 115 on the growth surface 114 of the substrate110 b are not cone-shaped, but closer to bullet-like shaped.

FIG. 11 is a schematic diagram of a light emitting diode chip of anothercomparative example of the disclosure. Referring to FIG. 11, the lightemitting diode chip 100E and the light emitting diode chip 100C aresubstantially the same; a major difference between the two lies in thatthe substrate 100A does not have a patterned surface; instead, the lightemitting diode chip 100A has a planar surface. Herein, the lightemitting diode chip 100E serves as a control reference of theenhancement of the output powers of the light emitting diode chips 100C,100D, wherein the parameter settings, the test method and enhancementcalculation method can be referred to the previous embodiments, anddescriptions thereof will be omitted hereinafter.

In the above embodiments, the microstructures are exemplified byprotrusions; however, it should be understood that the above embodimentsare presented by way of examples and not by way of limitation. Referencewill now be made in detail to other embodiments of the application.Whenever possible, components that are the same as those of the previousembodiment are assigned with the same reference numerals, anddescriptions thereof will be omitted hereinafter.

FIG. 12 is a schematic diagram of a light emitting diode chip of anotherexemplary embodiment of the disclosure. FIG. 13 is a partial top viewdiagram of a growth substrate in FIG. 12. Referring to both FIGS. 12 and13, the light emitting diode chip 100F and the light emitting diode chip100 are substantially the same; a major difference between the two liesin that the microstructures of the light emitting diode chip aredepressions 117, wherein the depth DP of each depression is between 1micron and 3 microns. In one exemplary embodiment, the depth DP isbetween 1.2 micron and 2 microns.

More particularly, each depression 117 has an opening 118 connected withthe growth surface 111, wherein the opening 118 has a width W1. In thisexemplary embodiment, each depression 117 has a plurality of sectionalsurfaces SEC2 (one of which is schematically depicted in FIG. 1)parallel to the growth surface 111, wherein the areas of these sectionalsurfaces SEC2 progressively decrease, for example, linearly decrease,along the depth direction. In this exemplary embodiment, each depression117 has a triangular pyramid shape, for example; however, it should beunderstood that the shape of the depression 117 is presented by way ofexamples and not by way of limitation. In other exemplary embodiments,the depression 117 has other cone shape, which can be attuned accordingto the actual design requirements. On the other hand, the area of thegrowth surface 111 occupied by these depressions 117 is A1, while thearea of the growth surface 111 not occupied by these depressions 117 isA2, wherein A1 and A2 satisfy the relation 0.1≦A2/(A1+A2)≦0.5.

In this embodiment, the two neighboring openings 118 maintain a distanceS1, and the sum of the width W1 and the distance S1 is a fixed value,ranging between 1 micron and 3 microns, wherein the sum of the width Wand the distance S is substantially identical to the distance G betweenthe centroids of two neighboring openings 118. Since the sum of thewidth W and the distance S is a fixed value, changes in the width W andthe distance S affect the value of the filling ratio (which isA2/(A1+A2)). Alternatively speaking, when the width W increases, thedistance S1 correspondingly decreases. Consequently, the area of thegrowth surface 111 occupied by the depressions 117 increases and thearea of the growth surface 111 not occupied by the depressions 117decreases to reduce the filling ratio. As the filling ratio decreases,the light emitted from the light emitting layer 122 is effectivelyscattered by these depressions 117; hence, the probability that acomplete reflection occurring inside the light emitting diode chip 100is reduced to thereby enhance the light extraction efficiency of thelight emitting diode chip 100F.

In other exemplary embodiments, a surface treatment is performed on thesurface of each depression 117 and the growth surface 111 to render thesurface of each depression 117 and the growth surface 111 with anappropriate degree of roughness. In principle, the surface roughness ofthe surface of each protrusion 112 and the growth surface 111 does notexceed the roughness value of 10 nm. When the surface roughness of thesurface of each protrusion 112 and the growth surface does not exceed 10nm, the epitaxy quality of the light emitting diode element layer 120 isimproved to ensure the light emitting efficiency of the light emittingdiode chip 100.

FIG. 14 is a schematic diagram of a light emitting diode chip accordingto another exemplary embodiment of the disclosure. Referring to FIG. 14,the light emitting diode chip 110G is, for example, a flip-chip lightemitting diode chip, and it is substantially the same as the lightemitting diode chip 100F. One major difference between the two lies inthat the light emitted from the light emitting diode chip 100G to theoutside is in a direction that passes through the substrate 110. In oneexemplary embodiment, the light emitting diode element layer 120 afurther includes a reflective layer 128. The reflective layer 128 isdisposed on the transparent conductive layer 127, and the transparentconductive layer 127 is positioned between the reflective layer 128 andthe second conductivity type semiconductor layer 123. Generallyspeaking, the material of the reflective layer 128 may include silver,aluminum, or other metals with favorable reflective property. When thelight emitted from the light emitting layer 122 is irradiated to thereflective layer 128, the light is reflected and transmitted toward thesubstrate 110.

According to the disclosure, the growth surface of the substrate of thelight emitting diode chip has a plurality of microstructures thereon,wherein the ratio of the area of the growth surface not covered by thesemicrostructures to the total area of the growth surface is between 0.1and 0.5 (which is the filling ratio is between 10% and 50%).Accordingly, the light emitted from the light emitting layer iseffectively scattered after being in contact with these microstructuresto lower the probability of a total reflection occurring internally ofthe light emitting diode chip to thereby elevate the light extractionefficiency of the light emitting diode chip. Alternatively, when thefilling ratio approaches 10%, the enhancement of the output power of thelight emitting diode chip is even more apparent. As the heights of theprotrusions increase, the enhancement of the output power of the lightemitting diode chip correspondingly increases.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the structure of thedisclosure without departing from the scope or spirit of the disclosure.In view of the foregoing, it is intended that the disclosure covermodifications and variations of this disclosure provided they fallwithin the scope of the following claims and their equivalents.

What is claimed is:
 1. A light emitting diode chip comprising: asubstrate comprising a growth surface and a plurality of microstructureson the growth surface, wherein a surface roughness of the growth surfacedoes not exceed 10 nanometers; and a light emitting diode element layerdisposed on the growth surface.
 2. The light emitting diode chip ofclaim 1, wherein the plurality of microstructures comprise a pluralityof protrusions, wherein a shape of one or more protrusions of theplurality of protrusions is oval, triangular, rectangular or polygonal.3. The light emitting diode chip of claim 1, wherein the light emittingdiode element layer comprises: a first conductivity type semiconductorlayer disposed on the growth surface; a light emitting layer disposed onthe first conductivity type semiconductor layer; and a secondconductivity type semiconductor layer disposed on the light emittinglayer.
 4. The light emitting diode chip of claim 3, wherein the lightemitting diode element layer further comprises: a first electrodeelectrically connected with the first conductivity type semiconductorlayer; and a second electrode electrically connected with the secondconductivity type semiconductor layer.
 5. The light emitting diode chipof claim 4, wherein the light emitting diode element layer furthercomprises: a transparent conductive layer disposed on the secondconductivity type semiconductor layer, wherein the second electrode iselectrically connected with the second conductivity type conductor layerthrough the transparent conductive layer.
 6. The light emitting diodechip of claim 5, wherein the transparent conductive layer comprisesindium tin oxide (ITO), indium zinc oxide (IZO), or metal oxide.
 7. Thelight emitting diode chip of claim 5, wherein a thickness of thetransparent conductive layer is greater than 0.03 micron.
 8. The lightemitting diode chip of claim 5, wherein a thickness of the transparentconductive layer is between 0.03 micron and 0.3 micron.
 9. The lightemitting diode chip of claim 5, wherein the light emitting diode elementlayer further comprises: a reflective layer disposed on the transparentconductive layer, wherein the transparent conductive layer is disposedbetween the reflective layer and the second conductivity type conductivelayer.
 10. The light emitting diode chip of claim 9, wherein thereflective layer comprises silver or aluminum.
 11. The light emittingdiode chip of claim 1, wherein a surface roughness of a surface of eachmicrostructure of the plurality of microstructures does not exceed 10nanometers.
 12. The light emitting diode chip of claim 1, comprising aflip-chip light emitting diode (LED) chip, a vertical type lightemitting diode (LED) chip, or a horizontal type light emitting diode(LED) chip.
 13. A method of fabricating a light emitting diode chip,comprising: providing a substrate, wherein the substrate comprises agrowth surface and a plurality of microstructures on the growth surface,wherein a first area of the growth surface occupied by the plurality ofmicrostructures is A1 and a second area of the growth surface notoccupied by the plurality of microstructures is A2, and wherein A1 andA2 satisfy the relation 0.1≦A2/(A1+A2)≦0.5; and disposing a lightemitting diode element layer on the substrate.
 14. The method of claim13, wherein the plurality of microstructures comprise a plurality ofprotrusions, wherein a shape of one or more protrusions of the pluralityof protrusions is oval, triangular, rectangular or polygonal.
 15. Themethod of claim 13, wherein the light emitting diode element layercomprises: a first conductivity type semiconductor layer disposed on thegrowth surface; a light emitting layer disposed on the firstconductivity type semiconductor layer; and a second conductivity typesemiconductor layer disposed on the light emitting layer.
 16. The methodof claim 15, wherein the light emitting diode element layer furthercomprises: a first electrode electrically connected with the firstconductivity type semiconductor layer; and a second electrodeelectrically connected with the second conductivity type semiconductorlayer.
 17. The method of claim 16, wherein the light emitting diodeelement layer further comprises: a transparent conductive layer disposedon the second conductivity type semiconductor layer, wherein the secondelectrode is electrically connected with the second conductivity typeconductor layer through the transparent conductive layer.
 18. The methodof claim 17, wherein the transparent conductive layer comprises indiumtin oxide (ITO), indium zinc oxide (IZO), or metal oxide.
 19. The methodof claim 17, wherein a thickness of the transparent conductive layer isgreater than 0.03 micron.
 20. The method of claim 17, wherein athickness of the transparent conductive layer is between 0.03 micron and0.3 micron.
 21. The method of claim 17, wherein the light emitting diodeelement layer further comprises: a reflective layer disposed on thetransparent conductive layer, wherein the transparent conductive layeris disposed between the reflective layer and the second conductivitytype conductive layer.
 22. The method of claim 21, wherein thereflective layer comprises silver or aluminum.
 23. The method of claim13, wherein a surface roughness of a surface of each microstructure ofthe plurality of microstructures does not exceed 10 nanometers.
 24. Themethod of claim 13, wherein a surface roughness of the growth surfacedoes not exceed 10 nanometers.
 25. A light emitting diode chipcomprising: a substrate comprising: a plurality of recesses; and aplurality of protrusions connected between the plurality of therecesses; and a light emitting diode element layer disposed on theplurality of the recesses and the plurality of the protrusions, whereina surface roughness of a surface of one of the recesses does not exceed10 nanometers.
 26. The light emitting diode chip of claim 25, wherein asurface roughness of a surface of one of the protrusions does not exceed10 nanometers.